Table 1.

Features extracted from the ECG and the PPG signal, together with their unit.

#	Name of Features	Calculation	Unit
1	Pulse Transit Time (PTT)	Time interval between ECG R peak and the maximum slope of PPG signal in the same heart cycle.	second
2	Heart Rate (HR)	60 (s/min) divided by the time interval (s) between the ECG R peaks.	beats per minute
3	Reflection Index (RI)	$\frac{b}{a}$	arbitrary unit
4	Systolic Timespan (ST)	$t{n}_n-t{f}_n$	second
5	Up Time (UT)	$t{p}_n-t{f}_n$	second
6	Systolic Volume (SV)	$\underset{t{f}_n}{\overset{t{n}_n}{{\displaystyle \int }}}PPG\left(t\right) dt$	arbitrary unit
7	Diastolic Volume (DV)	$\underset{t{n}_n}{\overset{t{f}_{n+1}}{{\displaystyle \int }}}PPG\left(t\right) dt$	arbitrary unit